For tightening screw connections with a predefined torque, use is increasingly being made of assembly wrenches that in addition to or instead of having a conventional measuring device for measuring and displaying the torque exerted on the screw joint have an integrated angle measuring device with an angle display which measures and displays the angle by which the assembly wrench has been turned. The angle by which the assembly wrench has been turned is measured in that case, for example, by a gyrometer integrated in the assembly wrench.
With assembly wrenches of that kind it is possible, by pretightening the screw connection using a slight torque and subsequently turning the assembly wrench by a defined rotation angle, to produce screw connections in which the preload force of the screw connection moves within a smaller tolerance range than in the case of tightening using a conventional assembly wrench which directly measures and displays the tightening torque applied to the screw connection or “slips” if a predefined tightening torque is exceeded.
In order to ensure a constant quality of the screw connections produced in that manner, regular checking and, where appropriate, calibration of the angle measuring device integrated in the assembly wrench is required.
Hitherto-known methods for checking and calibrating such assembly wrenches are either so complicated that they require the assembly wrench to be sent in to the manufacturer, and therefore are tedious and costly, or they do not have the requisite accuracy, such as, for example, checking of the angle display with so-called angle disks.